Topic: iTunes File Size Increase with Mountain Lion?

I recently retired the old MBP running Snow Leopard in favour of a new MBA.

I moved the data over from a backup on an external HD. The size of the iTunes library when viewed within iTunes is the same as it was on the old machine, but Daisydisk is showing the iTunes file size now being 20GB bigger than that. (I went to Daisydisk to try to find out why the total amount of stuff on the HD went from 88GB to 144GB in the move!)

OK, have now had the chance to run Daisydisk on both the new and old MacBooks.

It looks like the culprit is definitely somewhere in the iTunes folder.

Both machines are running iTunes 11.04 (4). The size of both song libraries is 58.7GB. However, the total iTunes folder on the old MBP, running OSX 10.6.8, is 60.1GB, while on the new MBP running 10.8.4 the folder size is 72.7 GB, despite the contents of the iTunes folders being identical.

After transferring everything over, did you open up iTunes to manage the new library? If so, did you stop iTunes from scanning tracks for playback levels along with stopping it from looking up album art (they are two separate processes)?

No, I didn't. Does that mean that the extra volume could be Album art that wasn't on the older Mac?

Depending on how many albums you have, album art can add quite a bit of heft to a library. The same goes for gapless playback information along with volume playback levels (if you use SoundCheck). A single album art image normally takes up about 1.5-2MB. Multiply that out by the amount of albums (not songs as each song in an album uses the same linked image) you have and it could account for some of the bloat. All-in-all, an extra ~12GB is nothing too bad. You could always remove the library from your new system and move it back manually without software. I don't see a need for using software to copy over an iTunes library when it can be done manually rather easily.